quorneng
Master member
Quite some time ago, actually 1974, I built a Depron XB70 Valkyrie.
Using a 70mm EDF that exhausting through 6 scale jet pipes.
Very light so an easy hand launch and belly land. To my surprise it actually flew very well and it still flies 10 year later.
I recently came across the XF108 mach 3 interceptor fighter also designed by North American.
Obviously it shared some of the same characteristics so I wondered if it would fly as well. It certainly "looks the part".
It was actually never built although North American spent a lot of time and money on development as the need to intercept bombers disappeared when it became obvious that ICBMs would be the nuclear threat.
Unlike the XB70 where two physical examples were built the detail design of the XB108 was never finally fixed so there are significant differences in the available 3 view drawings. This means that what ever I build will be wrong!
North American did build a full scale "mock up" but as it was top secret at the time there are only a few pictures of it.
But it does give a 3 dimensional picture of what it would look like.
An important feature is the huge inlets. With the exhaust nozzle petals closed to mach 3 configuration the area of the inlet is quite adequate to feed an EDF. An unusual combination for a turbojet powered plane. I note that there are drawings that show much smaller inlets.
My idea is to build it like the XB70 as a light weight hand launch/belly lander out of 3mm XPS foam sheet using a pair of 40mm EDFs although those big under wing fins could be an issue.😟
We shall see.

Using a 70mm EDF that exhausting through 6 scale jet pipes.

Very light so an easy hand launch and belly land. To my surprise it actually flew very well and it still flies 10 year later.
I recently came across the XF108 mach 3 interceptor fighter also designed by North American.

Obviously it shared some of the same characteristics so I wondered if it would fly as well. It certainly "looks the part".
It was actually never built although North American spent a lot of time and money on development as the need to intercept bombers disappeared when it became obvious that ICBMs would be the nuclear threat.
Unlike the XB70 where two physical examples were built the detail design of the XB108 was never finally fixed so there are significant differences in the available 3 view drawings. This means that what ever I build will be wrong!
North American did build a full scale "mock up" but as it was top secret at the time there are only a few pictures of it.

An important feature is the huge inlets. With the exhaust nozzle petals closed to mach 3 configuration the area of the inlet is quite adequate to feed an EDF. An unusual combination for a turbojet powered plane. I note that there are drawings that show much smaller inlets.
My idea is to build it like the XB70 as a light weight hand launch/belly lander out of 3mm XPS foam sheet using a pair of 40mm EDFs although those big under wing fins could be an issue.😟
We shall see.